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Tuesday, March 12, 2013

How Winner Cells Kill Loser Cells: New Perspectives

There are literally many trillions of cells in the human body. Every day, 20 to 70 billion of those cells die while others continue to survive and proliferate. Some cells die spontaneously through programmed cell death, a process known as apoptosis.

Specialized cells known as phagocytes, which act like vultures, then engulf and consume the byproducts of dead cells.

Some cells are actively destroyed by other cells. The cells that are victorious can be referred to as winner cells and those that die off can be referred to as loser cells. In many ways, cellular life is like real-world animal life, with daily competition where the strongest and/or best survives. Cellular competition is important because it helps get rid of deficient or damaged cells (caused by mutations) that can cause harm to the organism.

In a recent article published in BioEssays, researchers from Spain discussed recent results of cellular competition studies. They reinterpreted previous models of cell competition where winner cells were believed to be the ones that killed and engulfed the remains of loser cells. In the reinterpreted model, the winner cells identify kills the vulnerable loser cells (like an assassin of predator would) but recruit other cells to engulf their remains.

The article discussed how cell competition involves cells comparing their fitness status. In other words, the cells size each other up like two animals in the wild and the unfit cells are labeled with a molecular code that describes it as such. It as if these cells each have a sign on them saying “I’m a problem cell.” It is not precisely known how this code is recognized by other cells but in the end, the fit cells try to eliminate the unfit type.

While a defective cell can be eliminated by fit cells around it (akin to being someone being ostracized from a group) there are other times when a supercompetitor cell can overtake those around and spread (akin to an alpha male who destroys his surrounding competition and then spreads his lineage).

In some cases, however, such as cancer, the defective cells are protected by a special protein so that they are not eliminated. In this way, unfit cells can eventually overtake fit cells. In this way, disease can overtake the human body. For example, cancer is an abnormal growth of new tissue characterized by uncontrolled growth of abnormally structured cells that have a more primitive form.

Suggested reading: Molecular and Cell Biology For Dummies

Reference: Lolo FN, Tintó SC, Moreno E. (2013, in press). How winner cells cause the demise of loser cells: Cell competition causes apoptosis of suboptimal cells: Their dregs are removed by hemocytes, thus preserving tissue homeostasis. Bioessays.

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